The meteoric rise in bitcoin has meant that within the space of four years, one Norwegian man’s $27 investment turned into a forgotten $886,000 windfall.

Kristoffer Koch invested 150 kroner ($26.60) in 5,000 bitcoins in 2009, after discovering them during the course of writing a thesis on encryption. He promptly forgot about them until widespread media coverage of the anonymous, decentralised, peer-to-peer digital currency in April 2013 jogged his memory.

Bitcoins are stored in encrypted wallets secured with a private key, something Koch had forgotten. After eventually working out what the password could be, Koch got a pleasant surprise:

"It said I had 5,000 bitcoins in there. Measuring that in today's rates it's about NOK5m ($886,000)," Koch told NRK.